Bella is going to be fine! It's just a locking stifle! I never would have thought it, because the most obvious sign was that her leg was giving out, not locking. But in reality it was locking and unexpectedly unlocking. There are a couple different types of very minor surgery that can be done, but Bella shouldn't need that. She just needs conditioning to get her quadriceps strengthened, and it should stop happening. "Start riding her," was the suggested treatment. :)
Dr. Dave Rustebakke is "gifted with lameness" is what my sister told me. Well, I know I'm happy with him! And his prices are about the best I've personally seen. I'm really glad I didn't go to WSU. Their quote was 500% to 1000% more (yep that's a thousand), and I bet they would have been twitching their little student fingers to do the surgery, and probably would have told me it was the best thing to do.
Oh, and going down the grade with the trailer was no problem at all. Last time I must have had my trailer brakes adjusted incorrectly.